With a Burst of Energy: Glass That Amplifies Light

All About Glass

It was an idea that might have remained buried in scientific journals. Instead, it led to a device that gave modern telecommunications a much-needed boost.

In the 1960s, Elias Snitzer, a physicist at American Optical, added rare earth elements to glass. These elements can absorb light energy—and, he discovered, also amplify it, emitting large amounts of power at a single wavelength. Snitzer had invented the glass laser. Other lasers were more practical for most uses, but Snitzer realized that his had one advantage: glass that amplifies light—an optical amplifier—could be made in any size and shape.

Twenty years later, telecommunications was at an impasse. The electronic devices used to boost light signals traveling through optical fibers had reached their limit. Glass optical amplifiers were just what was needed to meet the demand for more and better communication. Faster and more powerful, they could efficiently amplify light signals up to 10,000 times.

How an optical amplifier works

An optical amplifier consists of a tiny “pump” laser and a short segment of glass fiber that contains the rare earth element erbium. The erbium absorbs the pump laser’s energy and stores it until the passing signal stimulates it release. The newly released light energy mimics the message-carrying signal. The extra light is then added to the signal as it moves on, strengthening it up to 10,000 times.

Boosting the signal

The first long-distance fiber-optic telecommunications systems used electronic amplifiers to strengthen the message-carrying signal. But electronic amplifiers are inefficient. The light must be converted into an electronic signal before it can be amplified. More modern systems—such as those that connect continents under the oceans—use optical amplifiers to boost the signal directly.

The Corning Museum of Glass
This article was originally published in Innovations in Glass, 1999, pp. 44–45.